Executive Producer Nikki Wilson says: “We are absolutely thrilled to introduce Sarah Jane and the gang to both the Eleventh Doctor and Jo Grant, and to have a script written by Russell T Davies is the icing on the cake.

“Viewers are in for a real treat, with an action-packed story full of Russell’s usual wit and warmth, which takes the gang inside a secret base beneath Snowdon and introduces brand new aliens, the mysterious Shansheeth. All this, plus a trip to an alien planet – a first for The Sarah Jane Adventures.”

Matt Smith says: “The opportunity to appear in The Sarah Jane Adventures came along towards the end of filming the first series of Doctor Who and I jumped at the chance.

“I knew Russell was going to write it, I’m very fond of Lis, she’s just lovely, and it’s a privilege to be working with two former companions. I felt such a bond working with the actresses and loved picking their brains about working with their Doctors in the past.”

Commenting on working with Matt, Lis Sladen adds: “He’s such an inclusive actor… He just had a week and he was really, really good. I think people will love it actually.”